Air-borne chemicals help clean atmosphere

Friday 07th Jan 2011 by theWeather Club

Have you ever wondered what actually happens to all of that pollution once we have pumped it into the atmosphere? Apparently some of it - though clearly not enough - simply disappears. An international research team led by the US based National Oceanic and Atmospheric Administration has taken a significant step forward in understanding the atmosphere’s ability to cleanse itself of certain pollutants. The whole issue has been highly contentious for many years, with some studies suggesting that the self-cleaning power of the atmosphere is fragile, while others suggest it is more robust.

New analysis published online in the journal Science shows that global levels of the hydroxyl radical - a critical player in atmospheric chemistry - do not vary much from year to year. The hydroxyl radical is central to atmospheric chemistry. Among other things, it reacts with and destroys the powerful greenhouse gas methane and air pollutants including hydrocarbons, carbon monoxide and sulphur dioxide but not - unfortunately - carbon dioxide. The new study has found that hydroxyl levels fall and rise by only a few percent every year, not by up to 25% as was once thought. It means that the study’s findings appear to come down on the side of the cleansing process being fairly stable.

“The new hydroxyl measurements give researchers a broad view of the ‘oxidizing’ or self-cleaning capacity of the atmosphere,” said Stephen Montzka, the study’s lead author and a research chemist at the Global Monitoring Division of NOAA’s Colorado facility. “Now we know that the atmosphere’s ability to rid itself of many pollutants is generally well buffered or stable,” Montzka continued. “This fundamental property of the atmosphere was one we hadn’t been able to confirm before.”

Previous estimates of hydroxyl levels swung wildly, leaving researchers unsure whether the discrepancies were due to errors in the estimation process, or to real swings in hydroxyl levels. It was an important issue to resolve. Large fluctuations in hydroxyl radicals would mean the atmosphere’s self-cleaning ability was very sensitive to human-caused or natural changes in the atmosphere. The group’s findings improve confidence in projecting the future of Earth’s atmosphere.

“Say we wanted to know how much we’d need to reduce human-derived emissions of methane to cut its climate influence by half,” Montzka said. “That would require an understanding of hydroxyl and its variability. Since the new results suggest that large hydroxyl radical changes are unlikely, such projections become more reliable.”

So if the atmosphere really is heading off to hell in a hand-basket, we can now make a much better guess of exactly when we’ll get there.